Getac Technology Corporation RX10RFID Manual De Usuario

SLAVE

SELECT

MISO

MOSI

DATA

CLK

WRITE

ADDRESS BYTE

READ DATA

BYTE 1

READ DATA

BYTE n

DON’T CARE

No Data Transitions (All High or Low)

MISO

MOSI

DATA

CLK

WRITE

MOSI Transitions on Data Clock

Rising Edge

MOSI Valid on Data Clock Falling Edge

tSTE,LEAD

tLO/HI

b6…b1

tSU,SI

tHD,SI

1/fUCxCLK

tSTE,DIS

b6...b1

tVALID,SO

tSTE,LAG

tHD,SO

DON’T CARE

READ

Data Transition is on Data Clock

Rising Edge

MISO Valid on Data Clock Falling Edge

tSU,SO

NO DATA TRANSITIONS

(ALL HIGH/LOW)

Slave

Select

TRF7970A

www.ti.com

SLOS743K – AUGUST 2011 – REVISED APRIL 2014

6.10.5.1 Serial Interface Mode With Slave Select (SS)

The serial interface is in reset while the Slave Select signal is high. Serial data in (MOSI) changes on the
rising edge, and is validated in the reader on the falling edge, as shown in

Figure 6-19

. Communication is

terminated when the Slave Select signal goes high.

All words must be 8 bits long with the MSB transmitted first.

Figure 6-19. SPI With Slave Select Timing Diagram

The read command is sent out on the MOSI pin, MSB first, in the first eight clock cycles. MOSI data
changes on the rising edge, and is validated in the reader on the falling edge, as shown in

Figure 6-19

During the write cycle, the serial data out (MISO) is not valid. After the last read command bit (B0) is
validated at the eighth falling edge of SCLK, valid data can be read on the MISO pin at the falling edge of
SCLK. It takes eight clock edges to read out the full byte (MSB first). See

Section 5.3

for electrical

specifications related to

Figure 6-19

The continuous read operation is shown in

Figure 6-20

Figure 6-20. Continuous Read Operation Using SPI With Slave Select

Detailed Description

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